Universal serial bus power delivery (USB-PD) can enable a universal serial bus (USB) device, e.g., a system such as a portable computing device, to receive power from a power source. A system with multiple USB-PD enabled ports may permit more than one power source to be connected to the system at the same time. If different input power sources are connected to two distinct USB ports at the same time, the input power sources may cause damage to the USB device and/or to one another.